A Sampling Rate Converter (SRC) converts a signal from an input sampling rate to an output sampling rate while preserving the signal's quality.
One of the major issues of SRCs is the data flow control, meaning the capability of sustaining data generation on its output at the requested output sampling rate while using the available number of samples available on its input at input sampling rate.
The sampling rate converter data flow control mechanism regulates the data flow of the sampling rate converter so that the sampling rate converter will always be able to provide the requested number of samples on its output starting from a defined number of samples on its input.
Typically, sampling rate converters generate a defined number of samples on their output starting from a defined number of samples on their input. Their functionality is dependent on the sustainability of a defined exact ratio between the input and output sampling rate.
The typical SRC problem is that the ratio between the output and input sampling rates (sampling rate ratio) is different from the one supported by the SRC due to the limited accuracy of frequency synthesizers. In this case the SRC will start making errors due to either the lack of input samples for generating output samples (in case the actual sampling rate ratio is larger than the SRC supported sampling rate) or to too many input samples that cannot be stored for generating the requested number of output samples (in case the actual sampling rate is lower than the SRC supported sampling rate).